Seals are used between inner and outer wellhead tubular and/or tree head members to contain internal well pressure. The inner wellhead member may be a casing hanger located in a wellhead housing and that supports a string of casing extending into the well. A seal or packoff seals between the casing hanger and the wellhead housing. Alternatively, the inner wellhead member could be a tubing hanger that supports a string of tubing extending into the well for the flow of production fluid. The tubing hanger lands in an outer wellhead member, which may be a wellhead housing, a Christmas tree, or a tubing head. A packoff or seal, seals between the tubing hanger and the outer wellhead member.
A variety of seals of this nature have been employed in the prior art. Prior art seals include elastomeric and partially metal and elastomeric rings. Prior art seal rings made entirely or partially of metal for forming metal-to-metal seals are also employed. The seals may be set by a running tool, or they may be set in response to the weight of the string of casing or tubing.
If the bore or surface of the outer wellhead or treehead member is damaged, a seal would struggle to maintain a seal. The elastomeric portion can provide additional robustness to the seal to help maintain a seal or effect a seal. However, the elastomeric portion of the seal assembly may not have sufficient radial energization and may result in leakage, sub-optimal wiping, and less robustness in the seal in general.
A need exists for a technique that addresses the seal leakage, wiping, and robustness problems described above. The following technique may solve these problems.